1. Field of the Invention
The present invention relates to a component imaging method for imaging a component held in a component transfer head, a component imaging device, and a component mounting device having the component imaging device.
2. Description of the Related Art
There has conventionally been known a component mounting device that uses a mounting head to remove a component from a component feeder and mount the component on a loading point of a board. The component mounting device has a component imaging device, which captures an image of the component held in the mounting head before mounting the component on the board, and recognizes the state in which the component is held by the mounting head, to correct the loading position and the like of the component.
Japanese Patent Publication No. 4381764 (referred to as “patent literature” hereinafter), for example, discloses this type of component mounting device. The component mounting device of this patent literature includes a component imaging device having a line sensor and a plurality of lighting parts, wherein any of the lighting parts illuminates a component, with the component being moved at constant speed in a sub-scanning direction of the line sensor relative thereto. At this moment, for a specific component, an image thereof is imported by alternately using two of the lighting parts with different lighting conditions (lighting directions), with the component being moved at half the speed for moving the other components. This process can acquire an image that has double line images with the different lighting conditions that are lined up alternately. Then, when the line images with the same lighting condition are extracted from this image and synthesized, two component images with different lighting conditions can be acquired simultaneously by allowing the component pass once with respect to the line sensor.
The component mounting device disclosed in this patent literature is loaded in a head unit with a plurality of mounting heads arranged in a line. The head unit of the component mounting device holds a plurality of components at once and conveys the components from the component feeder to the board to efficiently mount the components onto the board. Furthermore, when recognizing the components, the component imaging device continuously captures images of the components by sequentially moving the components, held in the respective mounting heads, in the sub-scanning direction of the line sensor with respect to the line sensor as the head unit moves.
However, in addition to the component mounting device disclosed in this patent literature that has a plurality mounting head arranged in a line as described above, a component mounting device that has a plurality of mounting heads arranged in two lines has been proposed in recent years.
In the component mounting device having mounting heads arranged in two lines, two component images held in adjacent mounting heads are included in the same line image. For this reason, when optimum lighting intensities of these components are different from each other, it is difficult to acquire a component image of either one of the components at its optimum lighting intensity. In order to avoid this difficulty, the components can be run a number of times with respect to the line sensor while switching the lighting intensity of the lighting parts, but the component cannot be recognized efficiently.
The technology disclosed in the patent literature can be employed in order to solve such problems. In other words, an image on which line images of different lighting intensities are arranged alternately is acquired by alternately changing the lighting intensities to capture images of the both components while imaging the same line twice, and the line images with the same lighting intensity are extracted individually from this image and synthesized. This can simultaneously acquire two component images having different lighting intensities, by simply allowing the component to pass with respect to the line sensor once.
However, this method needs to obtain double line images in order to obtain two images having different lighting intensities, requiring twice as long to image the same line twice. Therefore, this method is not always adequate in terms of efficiently recognizing the component, and therefore has room for improvement.